Spark plugs



G. D. SUTER SPARK PLUGS April 25, 1961 Filed July 7. 1959 FIGI INVENTOR. GEoRee D. SUTER 7 SPARKPLUGS George D. Suter, Wauwatosa, wis -assignor to Globe- Union Inc., Milwaukee, Wis., a corporation of Delal' 1 Filed July 7, 1959, Ser. No. 825,554

2'Clalms. (Cl. 313-131) This invention relates to surface discharge spark plugs for low voltages wherein a separating body is arranged between the electrodes and the spark isformed over the free active surface of such'body. p

In plugs of this type the outer electrode is generally of cylindrical shape (often forming the outer shell of the plug) and the inner electrode, although of various shapes, is positioned so that its parts are uniformly spaced from the sparking end of the cylindrical outer electrode. When voltage is applied to the electrodes ionization and are breakdown will occur across the surface of the separating body between the electrodes at any one of many diiferent locations around thecylindrical outer electrode. During continued operation of, the plug the arc will tend to move angularly around the sparking end of the cylindrical outer electrode. I

This moving arc phenomenon is not objectionable in many installations and may be'desirabl'e in some since it tends to spread electrode erosion uniformly over the sparking faces of the electrodes. However, in some installations it is importantthe spark 'take place at a speciency.

5 2,981,860 Patented Apr. 25, test end. The electrode assembly 18 is mounted in the bore against shoulder '24 with forked end 16 of connector 1-4 connected to such assembly.

The principal feature of this invention resides in the electrode assembly comprising an outer sleeve-like ground electrode 26 and a center electrode 28 embedded in or in firm contact with a separating body 30 of insulating or semi-conductive material. Center electrode 28 has an axially extending body portion 32 with an enlarged head 33 drilled to have a press fit on forked end 16 of connector 14. To positively locate the arc, with respect to the terminals, I provide a radially extending portion 34 on center electrode 28 which terminates just .short ofouter electrode 26 (Fig. 2).

It is the object of this invention to provide a spark plug of the type described wherein the spark will al Ways occur along the same path over theseparating body between the electrodes. p

This objectis attained by a sparkplug having ahollow tubular first electrode with an insulating'or semi-conductive separating body disposed within such first elec-' trode. A second electrode is embedded in the separating tion of the spark, I provide an electrode extension coribody spaced from the first electrode. To fix the locanected to one of the electrodes andextendingtowards theother.v Such electrode extension is embedded in the L separating body andjterminatesat a point spaced a short distance from the other electrode so'that when voltage is applied to the electrodes a concentratedfield is pro- Thus, when voltage is applied at the terminals a concentrated electric field, is produced at the end of elec- "trode portion 34 causing ionization and are breakdown and the exposed end surface of electrode 26 lying the shortest distance away from the end of portion34. This results because the density of an electric field is inversely proportional to the square of the distance between the One way to make the electrode assembly described above is to first position the electrodes properly in a. jig which is capable of withstanding high temperatures without distorting The insulation material 30 is then introduced as a fine powder into the areas between the electrodes and the assembly is heated to the softening point of the insulating material and the softened material compacted around. the electrodes. The firing end of the assembly is finallyrprepared (after cooling) by v grinding or machining to, expose the electrodes surfaces and provide the desired surface gap over the insulating material.

-Although but one embodiment of the present invenv tion has been illustrated and described, it will be apparduced at the end of the electrode extension. This causes ionizationiand arc breakdown across a surface of the separatingbody between the. end of the electrode extension-and the electrode spaced from .it. Thus, by

properly positioning the spark plug in' a' cylinder'of an Within the cylinder. e} V I Other objects and advantages will be pointed out 11], orbe apparentfrom the-specification and claims, as will internal combustion engine, 'forexample, it is possible to I locate the spark and. maintain it at anydesired-locatione eat to those skilled in the art that various changes and modificationsmay be made therein without departing from the spirit of the invention or from the scope of the appended claims. a

ylclaim: ,d H V .1. In a low tension surface discharge spark plug, a

hollow'tubular first electrode, a'separating body dis-' v posed within and in contact with said first electrode and formingv a sparking surface flush with the outer end of 1 said first electrode, a second rod-likeelectrode embedded in said separating body concentric with and spaced from. said first electrode and having a surface flush 'with'the obvious modifications of theme embodiment shown in the drawings, in which:

Figs. 1 and 2 are a side .elevationpyiew (with parts a spark plug embodying my inventin broken away) and abottom plan view, respectively, of

70., pointmore closely spaced from said other electrode than v A steel'center terminal or stud illl sealed in-place sparking surface of said separating body, and an electrode extension connected to oneof saidelectrodes and extend ing towardsfthe other electrode, said electrode extension embeddedin saidgfseparating body and having a surface ,The particulareappfication of this inventiqnghown ubstantially flU Sh'WIth the sparking surface of saldisepa Tthe drawings is incorporated 'spa'rkp'lug'of standard i design, exceptifor novel differences set forth hereinafter.v

rating body, said electrode extension-terminating at a any'other' parts ofsaid electrodes so thatwhenvoltage is A applied to said electrodes a concentrated field is prodnced at the end of said electrode extension causing ionization and are breakdown across a surface of said separating body between the end of said electrodeextension and said other electrode.

2. In a low tension surface discharge spark plug, a cylindrical body of insulating material having a surface over which sparking may occur, electrodes in engagement with and embedded in said body to provide spaced exposed surfaces flush with said surface of said body, at least one of said electrodes having a portion of its exposed surface projecting therefrom and flush with said surface of said body so as to be more closely spaced than the remainder of said exposed surfaces to define a small area of said body surface over which all efi'ective sparking occurs.

References Cited in the file of this patent UNITED STATES PATENTS 936,507 Anderson Oct. 12, 1909 350,847 Fowler Mar. 1, 1910 10 1,905,957 Anderson Apr. 25, 1933 2,890,365 Major June 9, 1959 2,920,223 Peras Jan. 5, 1960 

